Abstract
It is important for rehabilitation exoskeletons to move with a spatiotemporal motion patterns that well match the upper-limb joint kinematic characteristics. However, few efforts have been made to manipulate the motion control based on human kinematic synergies. This work analyzed the spatiotemporal kinematic synergies of right arm reaching movement and investigated their potential usage in upper limb assistive exoskeleton motion planning. Ten right-handed subjects were asked to reach 10 target button locations placed on a cardboard in front. The kinematic data of right arm were tracked by a motion capture system. Angular velocities over time for shoulder flexion/extension, shoulder abduction/adduction, shoulder internal/external rotation, and elbow flexion/extension were computed. Principal component analysis (PCA) was used to derive kinematic synergies from the reaching task for each subject. We found that the first four synergies can explain more than 94% of the variance. Moreover, the joint coordination patterns were dynamically regulated over time as the number of kinematic synergy (PC) increased. The synergies with different order played different roles in reaching movement. Our results indicated that the low-order synergies represented the overall trend of motion patterns, while the high-order synergies described the fine motions at specific moving phases. A 4-DoF upper limb assistive exoskeleton was modeled in SolidWorks to simulate assistive exoskeleton movement pattern based on kinematic synergy. An exoskeleton Denavit-Hartenberg (D-H) model was established to estimate the exoskeleton moving pattern in reaching tasks. The results further confirmed that kinematic synergies could be used for exoskeleton motion planning, and different principal components contributed to the motion trajectory and end-point accuracy to some extent. The findings of this study may provide novel but simplified strategies for the development of rehabilitation and assistive robotic systems approximating the motion pattern of natural upper-limb motor function.
Highlights
Hemiplegia, or unilateral paresis, is currently reported to be one major cause of physical disability in the middle-aged and elderly (Paul et al, 2002; Gert et al, 2003)
Synergy 3 consists of a shoulder extension (SFE), a combination of a shoulder adduction followed by an abduction (SAA), and a combination of internal rotation followed by a slight external rotation (SIR)
Our results showed that the first four principal components can sufficiently represent the dynamical profile of upper limb joint angles, and principal components with different scales exhibited different contributions to the multijoint motion behaviors
Summary
Hemiplegia, or unilateral paresis, is currently reported to be one major cause of physical disability in the middle-aged and elderly (Paul et al, 2002; Gert et al, 2003). Patients often experience autonomic difficulties in daily life due to the unilateral motor dysfunction. Recent works on upper-limb robotic training experiments exhibited substantial improvements on joint motions in either the horizontal plane or threedimensional space for the patients of motor impairment with wearable exoskeletons (Kwakkel et al, 2008; Jarrassé et al, 2014). Exoskeleton technology has attracted extensive attentions for its noteworthy value of assisting multi-joint rehabilitation movement and daily life performance (such as reaching and grasping) (Frisoli et al, 2012). Pilot studies suggested that spatiotemporal motion patterns that well match the nature of upper-limb joint movement plays a key role in the long lasting effects in rehabilitation (Liu et al, 2018). Little is known how to effectively use kinematic synergies of upper limb movement in exoskeleton motion planning for motor assistive purpose
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
